Polarization for DNA detection


The use of sensitive and inexpensive biosensors have a great perspective as mobile sensor of disease. Gold nano-particles have extremely large scattering cross sections, enabling the detection of single sub 100nm particles with a standard dark field microscope, or dedicated device.

In our research, we detect a biomolecule (protein or DNA) by capturing the biomolecule between a capture gold nanosphere (GNP) and a label GNP. The wavelength at which maximum scattering occurs is different between an isolated particle, and two particles close to each other. Therefore by monitoring the color of the particles before and after introduction of analyte+label GNP, we can detect analyte concentration very sensitively. (see our article in press at: http://www.sciencedirect.com/science/article/pii/S0956566311003836). However, because of the size distribution in particles, smaller particles after hybridization of a second label GNP can look like a bigger particle without a label. Therefore we currently must scan the surface before and after hybridization, and measure the change to each spot.


An alternative possibility, is to measure the scattering response under different polarization after the hybridization process. In such case, regardless of size, dimers should have more prominent change in the scattering intensity when scanning over the polarization compared to single particles.



spectra from P to S polarization

Illustration of gold nano-rods in darkfield illumination of P and S polarized light, resulting in a color change (measured on our TIR setup).

We have recently implemented polarization control, both in a TIR-based setup, and in a dark field setup, and we would like to compare polarization based detection vs. color-change based detection. We will use SEM imaging to correlate these changes with actual dimer formation.



If you are interested in this assignment, please contact:

Dr. Ron Gill

Phone: 053 489 3161

Email: r.gill@utwente.nl

Ing. Robert Molenaar

Phone 053-489 3053

Email: r.molenaar@utwente.nl